The present invention relates to a linear actuator configured to produce a thrust for linear movement, and particularly to enhancement of the strength of the thrust of the linear actuator.
The linear actuator, which is frequently called a linear motor, is configured to move one of a magnet and a coil by utilizing a thrust produced by electrifying the coil arranged in a magnetic field generated by the magnet. An example of a linear actuator is disclosed in Japanese Patent Provisional Publication No. 2007-282475A (hereafter, referred to as JP2007-282475A). In JP2007-282475A, it is disclosed that a mover is formed such that a plurality of permanent magnets are linearly arranged and an S pole and an N pole are alternately arranged in such a manner that that identical poles face with respect to each other, and that the coil serving as a stator is arranged in a magnetic field generated by the permanent magnets. In this configuration, by controlling a direction of a current to be supplied to the coil, a thrust is caused through the magnetic field generated by the permanent magnets, and the mover (i.e., the permanent magnet) is moved linearly by the produced thrust.
Japanese Patent Provisional Publication No. HEI 10-313566A (hereafter, referred to as JP HEI 10-313566A) also discloses an example of an actuator which is similar to that disclosed in JP2007-282475A. The linear actuator disclosed in JP HEI 10-313566A is configured such that a permanent magnet is arranged as a stator and a coil is arranged as a mover.
Each of the linear actuators disclosed in JP2007-282475A and JP HEI 10-313566A is configured such that the N pole and S pole are alternately arranged in the lengthwise direction, and a coil is formed of a three-phase coil to which currents having different phases are supplied. For example, with regard to the linear actuator disclosed in JP HEI 10-313566A having the coil serving as the mover, the three-phase coil is formed of three coils integrally arranged in a moving direction, and the current to be supplied to one or two of the three coils is controlled in a predetermined sequence so that thrusts are sequentially produced on the three coils in the moving direction. As a result, the mover can be moved linearly and continuously.